Implement and Add Built in font changer on Supermium

[youself64github]

Is your feature request related to a problem? Please describe.
The built in font changer in Supermium allows any websites to change fonts without extensions on Supermium.

Describe the solution you'd like
Built in Font Changer in Supermium is faster and lighter than any fonts changer extensions. This allows any websites to change font to another fonts without extensions.

Describe alternatives you've considered
Firefox has built in option to change fonts in any websites without extensions.

Additional context
I tried searching "how to change font without extensions on supermium" in google. but it has no results about it. Most Font Changer extensions in Chrome makes websites run slow.

[win32ss]

A non-extension solution would interfere with the sandboxing of the renderers. But it could work if applied as a pref on renderer initialization. However there are many features and issues under consideration at this time.

[narinishi]

The Customise fonts functionality already provided by Chromium can be used for globally affecting sites which utilize generic font families.

I find the Stylus extension a reasonably performant option for otherwise changing fonts. It injects CSS at page load time.